Sorting cells based on their surface markers is an important capability in biology and medicine. Magnetic Activated Cell Sorting (MACS) has become widely used as a cell sorting technique because it allows the rapid selection of a large number of target cells. The applications of MACS span a broad spectrum, ranging from protein purification to cell based therapies. Typically, target cells are labeled through a superparamagnetic particle that is conjugated to a molecular recognition element (e.g. a monoclonal antibody) which recognizes a particular cell surface marker.
Application of MACS has typically been limited to pre-enrichment before fluorescence-based cytometry. Nevertheless, due to its high throughput compared to other methods such as Fluorescence Activated Cell Sorting (FACS), MACS is still a widely used technology.
Current MACS systems are capable of high-purity selection of the labeled cells. However, they operate in a “batch mode” where the non-target and target cells are sequentially eluted after the application of the external magnetic field. In other words, the cells attached to magnetic particles are held in place while the unattached cells are eluted. Then, after this first elution step is completed, the magnetic field that prevented the magnetic particles from being eluted is removed and the magnetic particles can be eluted and recovered to recover target cells.
In order to achieve higher throughput and higher recovery of the rare cells (or other target components), improvements on existing MACS systems are needed.